1. Field of the Invention
The present invention relates to a circuit interrupter for an electrical distribution system.
2. Related Prior Art
Presently available electronic circuit interrupters generally operate on D.C. power and thus require a power supply connected at the input to line and neutral leads of an electrical distribution system. In many cases, in the event of opening of the neutral lead, the D.C. output is lost and the circuit interrupter is rendered inoperative. This problem has been overcome in the circuit interrupters described in British Patent Specification No. 2,000,398 (Hazemeyer) and U.S. Pat. No. 4,598,331 (Legatti) by use of an earth terminal or lead. In these arrangements, the earth lead is connected to the power supply to take over the function of the neutral lead if the latter becomes open. The earth lead also completes a path for activating current of a circuit breaker in the circuit interrupter.
While these arrangements may be suitable where earth leads are readily available, they are not satisfactory where an earth lead may not be available such as in double insulation equipment.
In an effort to provide continuing fault protection in the event of loss of neutral where an earth lead is not available, circuit interrupters have been devised having a circuit breaker which is normally activated and is de-activated when a fault occurs. This arrangement, however, suffers from the disadvantages that tripping will occur if the line voltage becomes low or absent and will fail to detect reversal of the line and neutral leads.